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An Insight into the Importance of Wrist Torque in Driving the Golfball: A Simulation Study

Eric J. Sprigings and Robert J. Neal

The purpose of this study was to examine whether, in theory, the clubhead speed at impact could be increased by an optimally timed wrist torque, without jeopardizing the desired club position at impact. A 2-D, three-segment model comprising torso, left arm, and golfclub was used to model the downward phase of the golf swing. Torque generators that adhered to the activation and force-velocity properties of muscle were inserted at the proximal end of each segment. Separate simulations were performed, with the wrist joint generator enabled then disabled. The results from these simulations showed that significant gains in clubhead speed (≈9 %) could be achieved if an active wrist torque was applied to the club during the latter stages of the downswing. For a swing that produced a clubhead speed of 44 m/s (≈99 mph), the optimal timing for the activation of wrist torque occurred when the arm segment was approximately 30° below a horizontal line through the shoulder joint. The optimal activation time for the joint generators was very much dependant on the shape of the torque profiles. The optimization process confirmed that maximum clubhead speed was achieved when the torque generators commenced in sequential order from proximal to distal.

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Student Learning as a Measure of Teacher Effectiveness in Physical Education

J. Len Gusthart and Eric J. Sprigings

The purpose of the study was to examine the effects of two experienced and expert teachers on the degree of student learning in a second grade physical education class. A systematic observation instrument (QMTPS) and number of practice trials were utilized to collect data on teaching behaviors. The experimental teachers were videotaped for later analysis over a 3-week period. Students were pretested and posttested to determine the extent of learning in selected force production and reduction skills. Analysis of the data showed that for three of the four force production and reduction skills, learning did occur in the experimental group. Process characteristics of the experimental teachers were described.

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The Choice between Bernoulli’s or Newton’s Model in Predicting Dynamic Lift

Eric J. Sprigings and James A. Koehler

This paper questions the appropriateness of using a model based on Bernoulli’s theorem to explain dynamic lift in sport. The authors discuss the relative merits of an alternative model based on Newton’s second and third principles.

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Factors Influencing the Performance of Springboard Dives of Increasing Difficulty

Doris I. Miller and Eric J. Sprigings

Major factors influencing the ability of divers to perform nontwisting springboard dives of increasing degree of difficulty were investigated. The analysis was based upon 49 dives (42 in pike and 7 in tuck) executed by male and female medalists in the 1996 Olympics. Videotapes were digitized to determine competitors’ vertical velocities and angular momenta at the beginning of dive flight. Centripetal force and resultant joint torque models were used to estimate the effort needed to perform multiple somersaulting dives. Increasing degree of difficulty by spinning in a pike rather than a tuck position for the same number of somersaults was associated with decreased vertical velocity at the start of dive flight, decreased angular velocity while somersaulting in a quasi-rigid position, and little change in centripetal force or related muscular effort. Increasing degree of difficulty by adding a somersault while rotating in a tuck rather than a pike position involved increases in vertical and angular velocities, a smaller increase in angular momentum, and notable increases in resultant joint torque and centripetal force. Sufficient muscular torque to maintain a compact spinning position was considered to be the major additional challenge facing divers making the transition from a 21/2 pike to a 31/2 tuck.

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Optimal Knee Extension Timing in Springboard and Platform Dives from the Reverse Group

Eric J. Sprigings and Doris I. Miller

Optimized computer simulation, using a mathematical model of a diver, was employed to gain insight into the primary mechanical factors responsible for producing height and rotation in dives from the reverse group. The performance variable optimized was the total angular displacement of the diver as measured from last contact to the point where the diver's mass center passed the level of the springboard or platform. The times of onset, and lengths of activation for the joint torque actuators, were used as the control variables for the optimization process. The results of the platform simulation indicated that the magnitude of the hip torque was approximately twice that generated by the knee joint during the early extension phase of the takeoff. Most of the knee extension for the simulation model coincided with the period of reduced hip torque during the later phase of takeoff, suggesting that the knee torque served mainly to stabilize the lower limbs so that the force from the powerful hip extension could be delivered through to the platform. Maintaining a forward tilt of the lower legs (~50° from the horizontal) during hip and knee extension appeared to be paramount for successful reverse somersaults. Although the movement pattern exhibited by the springboard model was limited by the torque activation strategy employed, the results provided insight into the timing of knee extension. Peak knee extension torque was generated just prior to maximum springboard depression, allowing the diver's muscular efforts to be exerted against a stiffer board. It was also apparent that the diver must maintain an anatomically strong knee position (~140°) at maximum depression to resist the large upward force being exerted by the springboard against the diver's feet. The optimization process suggested that, as the number of reverse somersaults increases, both the angle of the lower legs with respect to the springboard and the angle of knee extension at completion of takeoff should decrease.

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Optimizing the Release Conditions for a Free Throw in Wheelchair Basketball

Brianne N. Schwark, Sasho J. Mackenzie, and Eric J. Sprigings

The primary purpose of this study was to determine the optimal release conditions and corresponding arm movement pattern for the free throw for players classified as 3 to 4.5 on the international player classification system in wheelchair basketball. A 2-D, three-segment simulation model was used to investigate this problem. The computational process involved a two-step optimization scheme in which an outer computational loop was used to optimize the magnitude and timing of the muscle torques that generate the arm's motion, and an inner computational loop was used to determine the optimal angle and speed of the ball at the moment of release. The inner optimization loop revealed that Brancazio's (1981) and Hay's (1993) approaches to determining the optimal release angle produced identical results. The lowered seated height of the wheelchair basketball player required that the ball be released at a steeper angle with greater vertical velocity, and hence the need for greater shoulder torque. For the wheelchair player, the peak shoulder flexion torque generated by the model was reduced by approximately 43% when the upper arm was initially positioned at an angle approximately 40° below the horizontal, as compared to being positioned at an angle of 10° above the horizontal. For the wheelchair player, the optimal release angle and speed for a ball released at a horizontal distance of 4.09 m from the center of the basket, and 1.30 m below the rim, was computed to be 53.8° and 7.4 m/s, respectively.

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The Role of Shoulder and Hip Torques Generated during a Backward Giant Swing on Rings

Eric J. Sprigings, Joel L. Lanovaz, and Keith W. Russell

Backward giant swings on rings were performed by 2 elite gymnasts from both a stationary and a swinging handstand position. One of the ring cables was instrumented so that tension values could be recorded. Muscle torques and corresponding power profiles for the hip and shoulder joints were calculated and used to interpret the movement patterns displayed by the gymnasts. The hip-flexors played a primary role in preventing excessive hyper-extension of the hip joint during the downward swing. Overall, during the backward giant swing, the hip-joint flexors/extensors acted as a net energy sink for the system rather than as a source of energy generation. The piking motion that was observed to take place just past the bottom of the swing was primarily due to the momentum built up in the legs during the rapid straightening of the body during the bottom of the swing. The shoulder flexors/extensors functioned as the primary source of energy generation to the system. From a swinging handstand, with an initial handstand swing amplitude of 16°, the gymnasts were able to arrive at the next handstand position with approximately 6–7.5° of residual swing, which was close to the optimal value of 4° predicted by computer simulation.

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Development of a Model to Represent an Aluminum Springboard in Diving

Eric J. Sprigings, Denise S. Stilling, and L. Glen Watson

The purpose of this study was to develop a springboard model that could be used to predict, in future diving simulation studies, the vertical interaction forces between a diver’s feet and the board during the time of board depression and recoil. To achieve this, the characteristic parameters (effective mass, stiffness, and damping) for a Duraflex springboard were first examined using a finite element approach. The finite element results indicated that a linear model, consisting of a lumped mass and spring, could be used to simulate the actual dynamic behavior of a springboard system. The effects of damping on the board’s motion were found to be negligible and could safely be ignored. The values for the model’s parameters (board stiffness and effective board mass) were determined empirically and are reported in this paper.

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Measurement of the Modeling Parameters for a Maxiflex “B” Springboard

Eric J. Sprigings, Denise S. Stilling, L. Gien Watson, and Paul D. Dorotich

The characteristic modeling parameters (spring stiffness and effective mass ratio) were determined experimentally for a Maxiflex “B” board. The results indicated that the Maxiflex “B” board was substantially less stiff than a Duraflex board. Most of this decrease in stiffness is a result of the added second taper in the Maxiflex “B” board. Calculations, based on theory, revealed that the perforations in the Maxiflex “B” board reduced the local stiffness over the end region of the board by an additional 10%. As a result of its greater compliancy, the Maxiflex board also had an effective mass ratio that was greater than that of the Duraflex. It was clear from these experiments that the acknowledged superiority of the Maxiflex “B” board over the Duraflex could be attributed directly to the increased compliancy found in the Maxiflex “B” board.